Variable susceptance coaxial tuner



Sept. 5, 1967 w. N. CARON VARIABLE SUSCEPTANCE COAXIAL TUNER 2 Sheets-Sheet 1 Filed Aug. 12, 1965 //VVEN7'0R. Wilfred N.C0ron ATTOR Sept. 5, 1967 w. N. CARON 3,340,485

VARIABLE SUSCEPTANCE COAXIAL TUNER Filed Aug. 12, 1965 2 Sheets-Sheet i l/VVE/VTOR. Wilfred N.Coron V by 0% ATT United States Patent 3,340,485 VARIABLE SUSCEPTANCE COAXIAL TUNER Wilfred Norman Caron, Gardena, Calif., assignor to Dynalectron Corporation, Washington, DC, a corporation of Delaware Filed Aug. 12, 1965, Ser. No. 479,171 10 Claims. (Cl. 333-97) ABSTRACT or THE DISCLOSURE A tuner for a coaxial line is provided in which a ribbon may be fed through a slot in the outer conductor into the space between the'inner and outer conductors, to build up the diameter of the ribbon within the conductor to any desired extent. The outer conductor is slotted so that the ribbon may be slid along the length of the conductor to any desired location.

This invention relates to improvements in a coaxial tuner for continuously varying the radio frequency voltage amplitude and phase in a closed coaxial system without the use of sliding stub tuners, line stretchers and without in any way shorting the coaxial system with a shunt stub tuner.

Those familiar with the art of radio frequency propagation in a coaxial line are aware of the importance of obtaining an electrically flat line which minimizes mismatch and reactive losses. A general discussion of mismatch losses encountered in coaxial lines is given in Microwave Transmission Design Data, by T. Moreno, Dover Publishings, Inc., 1948.

It has been known in the prior art that compensation for reactive mismatches can be eifected by introducing into the coaxial line, a susceptance of proper value at a predetermined point in the line thus obtaining a maximally flat line electrically.

The chief objections to available coaxial line tuners such as the line stretchers and stub tuners is their poor sliding metal to metal contacts, poor mechaical rigidity, awkward size at low frequencies and obvious lack of high power handling.

The object of the invention is to provide an improved variable susceptance coaxial tuner which avoids the abovenamed objections.

A further object of this invention is to provide a novel form of susceptance device to enable tuning of a trans mission line without interchanging elements.

Further objects and advantages of the invention will appearfrom the hereinafter set forth detailed description when taken in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal view of a timer made in accordance with the invention.

FIG. 2 is a cross-sectional view of the tuner with a ribbon element thereof in a withdrawn position from the transmission line.

FIG. 3 is a similar view with the major portion of the ribbon element located within the transmission line of the tuner element.

FIG. 4 is an elevation of a modified form of tuner, and

FIG. 5 is an elevation of a tuner assembly with two variable susceptance units.

In the embodiment of the invention shown in FIGS. 1, 2, and 3, the tuner assembly generally indicated at has an inner conductor 12 surrounded by a dielectric sleeve 14 to prevent voltage breakdown under high power operation. The outer conductor is shown at 1-6 and is slotted longitudinally as shown at 18. The slot length is generally chosen to be a little more than one-half wavelength 3,340,485 Patented Sept. 5, 1967 at the lowest frequency of operation of the transmission line. Y

A ribbon 20 of a dielectric or conductive material, preferably the latter, has its inner end positioned within the outer conductor and is preferably provided with a thickened and rounded end piece 22 to prevent accidental complete withdrawal of the ribbon from the slotted conductor and to facilitate winding up of the ribbon into the conductor when the ribbon is thrust into the conductor via the slot. To facilitate accomplishment of this last purpose, the ribbon may be made of a fairly firm polyethylene or thin' brass or other non-magnetic material or of a mag netic material, including materials having ferritic propcities. The insertion of the ribbon into the conductor serves to vary the ratio of the diameter of the inner conductor 12 to the inside diameter of the ribbon spiral 24 thus thereby varying the susceptance magnitude. The ribbon may be slightly tapered in thickness near the ribbon end 22 to facilitate winding up of the ribbon. The outer end of the ribbon may be provided with a suitable thickened stop 26 to prevent thrusting the entire ribbon into the conductor.

As more of the ribbon 20 is pushed into the interspace region of the coaxial assembly, the ribbon will shape itself into the tight spiral 24. After adjusting the ribbon along the length of the slot to a desirable position to secure proper phase relationship, the amount of susceptance desired is governed by the length of the ribbon 20 inside the coaxial assembly 10. The width of the ribbon 20 and the inside diameter of the generated spiral 24 determine the magnitude of the susceptance introduced.

A modification of the tuner is illustrated in FIG. 4. In that figure there is disclosed a spool 27 with slotted hub 28 through which the end of the ribbon passes into the outer conductor. The free end of the ribbon is wound about the spool and when it is desired to feed the same into the conductor or withdraw the same, the tape mass on the bobbin is rotated. Thus proper storing of the ribbon and ease in feeding the same may be attained. To

vary the phase in the coaxial assembly, it is only necessary to move the spool 27 and metal ribbon spiral axially along the coaxial assembly, any desired distance between 0 and electrical degrees equivalent to one-half wave length of the transmitted wave. The half wave length is desirable to allow for inductive and capacitative reactances in the line. A tab or tabs 30 on the spool 27 is provided to facilitate moving the spool and ribbon along the line.

As a modification of the ribbon storing means, the spool may be replaced by a pair of discs 32, preferably of dielectric material, placed around the coaxial outer conductor 16 and between which the ribbon is wound, permitting coiling of the unused ribbon between the discs. The outer ribbon end 26 is looped and pinned in place by a pin 34 (see FIG. 5), secured in the two discs. A ring 36, preferably of dielectric material, is secured between and at the periphery the two discs, the ring and discs enclosing and forming a housing for the stored ribbon. Rotating the housing in a counterclockwise direction, for instance, inserts more ribbon into the coaxial assembly thus increasing the susceptance. Rotating the housing in the clockwise direction withdraws the ribbon from the coaxial assembly and reduces the susceptance.

For higher susceptance levels and/or better control of the amplitude and phase, a plurality of ribbons may be used for one coaxial assembly as shown in FIG. 5. Al though both ribbons are shown as insertable in the one slot, it is obvious that a separate slot may be provided for each ribbon. The coaxial tuner assembly may be connected into a transmission system under test by means of input and output connectors 38 and 40.

While there have been shown and described several forms of embodiment of the invention, other modifications may be made thereto which modifications are intended'to be claimed so long as they fall within the scope of the claims appended hereto.

What is claimed is:

1. In a transmission line, a tuner element comprising a hollow conductor having a slot in the wall thereof longitudinally of the conductor, and a ribbon inserted in said slot and coilable Within the conductor upon feeding of the ribbon through the slot.

2. The structure of claim 1 wherein the ribbon is of metal.

3. The structure of claim 1 wherein a second conductor is positioned coaxially within the hollow conductor and the ribbon is coilable in the space between the two conductors.

4. The structure of claim 3 wherein the ribbon is of metal and the second conductor has an insulating cover thereabout.

5. The structure of claim 1 wherein the slot in the wall of the conductor is longer than the width of the ribbon whereby the ribbon within the conductor may be shifted longitudinally of the conductor.

6. The structure of claim 1 in combination with a second ribbon, spaced from the first ribbon, inserted in a slot in the first conductor and coilable within the conductor.

7. The structure of claim 1 wherein guide means for the ribbon are mounted on the outer conductor.

8. The structure of claim 7 wherein the guide means is a spool having a hub provided with a slot parallel with the slot in the outer conductor.

9. The structure of claim 7 wherein the guide means comprises a pair of discs with a pin transversely of the discs rigidly holding the discs in spaced relationship, the free end of the ribbon being attached to said pin.

10. The structure of claim 9 'Wherein a ring is rigidly secured to the discs at the peripheral edge of the discs, the discs andring forming a-housing for the ribbon.

No references cited.

HERMAN KARL SAALBACH, Primary Examiner.

L. ALLAHUT, Assistant Examiner. 

1. IN A TRANSMISSION LINE, A TUNER ELEMENT COMPRISING A HOLLOW CONDUCTOR HAVING A SLOT IN THE WALL THEREOF LONGITUDINALLY OF THE CONDUCTOR, AND A RIBBON INSERTED IN SAID SLOT AND COILABLE WITHIN THE CONDUCTOR UPON FEEDING OF THE RIBBON THROUGH THE SLOT. 